Hydraulically integrated solids/liquid separation system and method for wastewater treatment

ABSTRACT

A system and method for treating wastewater includes a treatment container for receiving and treating wastewater and a mixing/aeration system disposed in the treatment container. Wastewater is pumped under pressure from the treatment container through a solids/liquid separation system, preferably comprising multiple parallel membrane bioreactors, to separate the solids and liquids in the wastewater. Liquid retentate from the solids/liquid separation system is cycled back to the treatment container via the mixing/aeration system. The closed-loop system and method for solids/liquid separation and aeration/mixing provides for reduced equipment requirements and energy usage during operation.

This application claims the benefit of U.S. Provisional Application No.60/672,755 filed on Apr. 19, 2005.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates generally to the field of treatment ofwastewater, and more particularly to an improved system and method fortreating wastewater containing contaminants, which system and methodoffer a broad array of advantages over conventional membrane bioreactorsand/or activated sludge wastewater treatment systems, including loweroperating costs, smaller size, better control of membrane fouling,higher rates of operation, high oxygen transfer efficiency, and adecreased level of excess sludge production.

With an increased awareness of problems with water quality, particularlythose caused by the discharge of wastewater from industrial sources, hascome a demand for improved equipment and methods to treat wastewaterprior to discharging it into a sewer, to surface water, reuse forirrigation, recycling or other “grey water” applications, or to otherdestinations for effluent discharge. While such treatment systems andmethods are generally not required to produce potable water, they areincreasingly required by law to enhance the quality of wastewater priorto discharging it as effluent. For industrial waste, this treatmentprocess must typically remove certain types of pollutants such asorganic contaminants, nitrogen and phosphorus, metals, and suspendedsolids.

The first wastewater treatment systems were of simple design, with asingle container or tank being used for both treatment of the wastewaterand the removal of solids from the wastewater, typically by allowingthem to settle out. These early wastewater treatment systems were notaerated, and typically generated foul odors as a byproduct of theprocess utilized by these systems. Over time, these early wastewatertreatment systems evolved into systems which use a popular type ofwastewater treatment process referred to as the activated sludgewastewater treatment method.

The conventional activated sludge wastewater treatment system and methoduse an aeration tank which is followed by a solids/liquid separatorwhich acts as a secondary clarifier to remove separated solids from theliquid, which is discharged by the system. As its name suggests, thecontents of the aeration tank are aerated and mixed to facilitate anaerobic reaction (a reaction taking place in the presence of oxygen)which is facilitated by the presence of activated sludge. This activatedsludge, which is an accumulation of microorganism-rich residue(“sludge”) contained in the solids which are separated from the liquidin the solids/liquid separator, is seeded into the incoming wastewaterin the aeration tank. In conventional activated sludge wastewatertreatment systems, the concentration of activated sludge solids istypically 2,000 to 5,000 milligrams per liter in the aeration tank.

The aerobic reaction which takes place in the aeration tank includesthree types of phenomena—absorption, adsorption, and biologicaldigestion. Any one of these three phenomena will result in contaminantsreacting with the bacteria contained in the activated sludge. Absorptiontakes place when a contaminant is absorbed into the cell wall of thebacteria contained in the activated sludge. Adsorption, on the otherhand, is a surface phenomenon which takes place when there is aninteraction between a contaminant and the surface of the activatedsludge whereby the contaminant adheres to the surface molecules thebacteria. Biological digestion takes place when the bacteria containedin the activated sludge consume waste constituents contained in thewastewater. Biological digestion can occur after the material has beenabsorbed or adsorbed. Other mechanisms of treatment that may be involvedinclude, but are not limited to, flocculation/coagulation,sedimentation, or enmeshment reactions that are induced by the activatedsolids.

As mentioned above, the reaction that takes place in the aeration tankis an aerobic reaction occurring in the presence of oxygen, whichdecreases both the amount of time required for the reaction to occur andthe level of foul odors produced by the reaction. Typically, aerationand mixing may be produced by injecting compressed air or oxygen intothe mixture, typically through diffuser devices located near the bottomof the aerator tank. As the air bubbles to the surface of the mixture,the diffused air provides both oxygen to the mixture and a vigorousmixing action. The amount of material contained in the wastewater may becharacterized by the “chemical oxygen demand” or COD of the material. Achemical oxygen demand of one pound indicates that the materialcontained in the wastewater requires one pound of oxygen to degrade.

Air may also be added by the churning action of mechanical mixerslocated near the surface of the mixture contained in the aeration tank.In still another variation, mixing of the contents of the aeration tankmay be caused by hydraulic pumping in which liquid is pumped out of thetank and back in through nozzles causing highly efficient mixing of thecontents of the aeration tank. In a still further variation, air nozzlesmay be arranged around the liquid nozzles to further stimulate themixing and simultaneously provide oxygen to the mixture. Still furthervariations include processes known as extended aeration and contactstabilization, both of which omit the primary settling step, andhigh-purity oxygen aeration, which can substantially reduce both theaeration time and the size of the aeration tank.

The conditions which are thus provided in the aeration tank promote thegrowth of the microorganisms introduced in the activated sludge with theresultant reaction removing contaminants from the wastewater. Inconventional activated sludge technology, a predetermined period of timerelated to the strength of the wastewater, kinetics, environmentalconditions and treatment objectives is required for the mixture to reactin the aeration tank in the process. This time is required to allow thebacteria in the aeration tank to react with the contaminants containedin the wastewater, with much of the material being oxidized by themicroorganisms. Generally, in conventional activated sludge processes,the contaminants are completely digested in the aeration tank.

In conventional wastewater treatment systems, the mixture is thenallowed to flow from the aeration tank into a solids/liquid separator,as described in more detail herein. For example, the solids/liquidseparator may be as simple as a secondary clarifier, which allowsactivated sludge to settle out by gravity. The clean liquid overflowsfrom the separator and it is discharged as secondary effluent, while theactivated sludge may be separated out in a settling tank. The bacteriatends to clump together and settle to the bottom of the settling tank,from which the activated sludge may be pumped out.

Some of the activated sludge will be recirculated back into the aerationtank, with this sludge being referred to as “return activated sludge” orRAS. The microorganisms contained in the return activated sludge arethus well acclimated to the environment in the aeration tank. Theremaining activated sludge is treated and disposed of in a conventionalsolids processing technique which is well known to those skilled in theart. This sludge is referred to as “waste activated sludge” or WAS. Inconventional activated sludge technology, the waste activated sludge mayamount to as much as seventy percent of the sludge recovered in thesolids/liquid separator.

The amount of excess activated sludge which is generated by an activatedsludge waste treatment system may be controlled by a term referred to as“solid retention time” or SRT, which is the amount of time an averageparticle of solid material remains in the waste processing system. Thesolid retention time is inversely proportional to the relative volume ofexcess activated sludge which must be disposed of. Conventional extendedactivated sludge waste processing systems (designed for surface waterdischarge of effluent) have a solid retention time of approximatelytwenty days.

The excess solids produced may be determined by the yield of theactivated sludge process multiplied by the mass of the contaminantsremoved. The yield may be measured in units of pounds of “chemicaloxygen demand” or COD, which is a term commonly used to measure theamount of contaminants which are removed. Conventional extendedactivated sludge waste treatment systems produce a yield ofapproximately 0.25 pounds of “total suspended solids” or TSS of excessactivated sludge per pound of chemical oxygen demand of yield. Lessconservatively operated systems can produce yields of 0.7 pounds oftotal suspended solids per pound of chemical oxygen demand removed.

The waste activated sludge is typically accumulated, and may be furtherbiologically processed and/or dewatered prior to its ultimate disposal.

Membrane bioreactors (“MBRs”) have been used more recently in wastewatertreatment as a means to improve upon conventional activated sludgewastewater treatment processes, combining the biological treatment, asdescribed above, with a membrane separation step. In particular, an MBRuses membranes, rather than settling, to separate and concentrate thebiomass by removing wastewater—eliminating the need for secondaryclarification and/or filtration.

Depending on the contents of the waste stream, the given systemrequirements and quality requirements of the effluent, the membranesutilized in an MBR can be of any type or porosity. Generally, MBRs caninclude reverse osmosis, nanofiltration, ultrafiltration,microfiltration and any other solids/liquid separation membranes knownto those skilled in the art. Thus, in addition to removing biodegradableorganics, suspended solids and inorganic nutrients, MBRs retainparticulate matter, remove a very high percentage of pathogens and/orremove dissolved materials from the wastewater.

Because the membranes act as substantially absolute barriers to thebacterial particulate and utilize a hydraulic pressure differentialacross the membrane as a separating mechanism, MBR systems operate athigher MLSS (mixed liquor suspended solids) concentrations overtraditional activated sludge systems as most of the biomass isrecirculated inside (or back to) the bioreactor—accordingly, thefootprint of an MBR system is often smaller than typical activatedsludge systems.

There are two types of MBR—a first type (“a submerged MBR”) in which themembrane unit(s) are mounted directly in the aeration tank of theactivated sludge treatment system and a second type (a “side stream” or“SS” MBR) in which the membrane unit(s) are external to the aerationtank. In the submerged MBR, the head pressure of the wastewater on theoutside of the submerged membranes provides lower but sufficientdifferential pressure to drive the wastewater through the membranes andconcentrate the biomass in the bioreactor. Typically, the head pressureis supplemented by a suction pump connected to the permeate outlet sideto create a higher differential pressure across the membranes. Toprevent fouling in a submerged system, cross-flow along the membranesurface is achieved using an airlift flow (air blowers and/or airspargers positioned in the aeration tank below the membranes).

In the external MBR system, the membrane modules are placed, typicallyin series configuration, downstream from the bioreactor. The biomass isdrawn from the bioreactor and pumped through the membranes wherewastewater is removed as permeate and suspended organic and mineralsolids, dissolved organic matter, and bacteria are retained and returnedto the bioreactor more concentrated. In this configuration, the biomassis pumped under pressure from the aeration tank through themembranes—such pump providing the differential pressure across themembrane.

While the MBR wastewater treatment systems and methods currently knownin the art present an advantageous way to remove contaminants fromwastewater, they do, however, present a number of disadvantages as well.First, by operating at high MLSS concentrations, the build-up of solidsat the membrane surface decreases permeability of the membranes, therebyincreasing the pressure needed to maintain the flux at acceptablelevels. Further, increasing the pressure required to maintain a highflux through the membrane increases the energy cost of system operation.In addition, membrane fouling requires periodic shutdown and/or chemicalcleaning of the membrane system—which can be disruptive to users of thesystem. Further, the membrane modules themselves are expensive.

In addition to these disadvantages, biological digestion/treatment andsolids/liquid separation have traditionally been viewed as two separateprocesses, and thus, current membrane bioreactor configurations (or anysolids/liquid separation system following biological treatment ordigestion) can include a significant amount of redundancy in equipment.For example, in addition to the pumps required to hydraulically mixand/or aerate the aeration tank, a separate vacuum and/or supply pumpmust be included to overcome dynamic losses through the membrane and tomaintain the desired operating pressure in the system. A furtherrecirculation pump from the membrane system back to the bioreactor tankis also required. Such configurations require a substantial amount ofenergy input, rendering these systems cost prohibitive in certainapplications.

In addition, solids/liquid separation systems, including MBRconfigurations, usually include an equalization tank/balance tank tohandle variation in the flows so that the MBR can be sized to treat theaverage daily flow to the system, rather than the peak daily flow.Accordingly, redundancy in equipment, including not only tanks andpumping equipment, but also monitoring and process control equipmentmandate a relatively large amount of space in which to installthem—thus, any wastewater treatment configuration that can reduce therequired system footprint of the wastewater treatment system would be asignificant economic and operational advantage. Further, a reduction inthe required equipment for such system can reduce the initial capitalcosts, installation costs and maintenance costs.

Also, as noted above, presently known activated sludge systems produce asubstantial amount of waste activated sludge which must be disposed of.This high disposal burden presents both storage problems and asignificant cost to transport the sludge away for disposal. Thus, itwill be appreciated that any wastewater treatment system that can reducethe amount of waste activated sludge would also be a significanteconomic and operational advantage.

Finally, operating an activated sludge system is a relatively complexprocess with a number of variables; it would be preferable to have asimpler system if possible.

It is accordingly the primary objective of the present invention that itprovide an improved waste processing system which is smaller andtherefore less expensive to initially purchase and install than aconventional activated sludge and solids/liquid separation system.

It is still another objective of the waste processing system of thepresent invention that it require less energy to drive the solids/liquidseparation system, hydraulically mix the aeration tank, and/or provideoxygen to the reaction to further reduce operating costs, and that it doso without adversely affecting either the biological digestion oforganic waste solids or the time required to achieve solids/liquidseparation. It is a still further objective of the waste processingsystem of the present invention that it present a simplified operatingprocess which is easy to operate and which presents relatively fewpotential problems in its day-to-day operation.

It is a closely related objective of the waste processing system of thepresent invention that it be capable of operating at a higher rate thancomparable conventional systems to deal with increased loads ofcontaminants, or to produce higher quality effluent, or both. It is anadditional objective of the waste processing system of the presentinvention that it produce a reduced amount of sludge, therebysubstantially reducing the cost of operation of the system.

The waste treatment system of the present invention must also be ofconstruction which is both durable and long lasting, and it should alsorequire little or no maintenance to be provided by the user throughoutits operating lifetime. In order to enhance the market appeal of thewaste treatment system of the present invention, it should also be ofinexpensive construction to thereby afford it the broadest possiblemarket. Finally, it is also an objective that all of the aforesaidadvantages and objectives be achieved without incurring any substantialrelative disadvantage.

SUMMARY OF THE INVENTION

The disadvantages and limitations of the background art discussed aboveare overcome by the present invention. With this invention, a wastewatertreatment system and method is provided in which an inline solids/liquidseparation system is integrated with a hydraulic mixing system and/or anaeration system, in order to achieve all of the objectives mentionedabove without incurring a single significant disadvantage. The presentinvention directs the output flow from the mixing system/aeration systempumps through the solids/liquids separation system before such outputwastewater is supplied to the mixing/aeration system. The presentinvention can be utilized in any wastewater treatment systemincorporating such a mixing system/aeration system and a solids/liquidsseparation system, and as such, may include any required mechanical,chemical and/or biological processing steps and/or be of virtually anydesign.

The solids/liquid separation system (SLS) used in the present inventioncan be any of those known to those skilled in the art including, but notlimited to, membrane technology (microfiltration, ultrafiltration,nanofiltration, reverse osmosis, biomedical filtration, etc.), barriers,centrifuges, cyclones and/or any inline process to affect separation ofsolids from the treated effluent.

In one aspect of the present invention, the solids/liquid separationsystem comprises a plurality of membrane modules arranged horizontallyin a parallel configuration with respect to the membrane feed pump. Thehydraulic mixing system is a jet aeration system and/or any mixingsystem known to those skilled in the art. Accordingly, the presentinvention integrates the feed pump of the jet aeration system with thesolids/liquid separation system such that the solids/liquid separationsystem does not require an independent suction pump and/or a supply pumpto drive wastewater through the membrane/SLS.

The present invention eliminates redundancy in equipment and controlscosts by operating the system in a substantially “closed loop” manner,wherein a pump may be used to supply both the hydraulic mixing systemand the solids/liquid separation system—taking advantage of the pressurehead of the wastewater in at least one of the wastewater treatment tanks(preferably, an aeration tank requiring jet aeration, an anoxictreatment vessel and/or an anaerobic treatment vessel requiringhydraulic mixing) to operate at a higher system pressure. Unlikeconventional systems, the SLS supply pump accounts for pressure lossesin the solids/liquid separation system (transmembrane pressure) and jetaeration system losses (loss through the aeration nozzle and lossassociated with hydraulic mixing), dynamic/frictional losses and/or anystatic lift losses associated with placement of the pump and the SLSsystem relative to the liquid head in the tank to be integrated.Accordingly, the wastewater treatment system of the present inventionuses less energy and is less expensive to operate than conventionalwastewater treatment systems. In addition, with the elimination of apumping system and/or one or more level, flow or pressurecontrol/balancing systems, the present invention is less expensive topurchase, install and maintain over prior art systems.

Accordingly, the present invention can comprise, in part, a wasteprocessing system for removing contaminants from wastewater. The systemcan comprise one or more containers for one or more of aerobicdigestion, anaerobic digestion, chemical treatment, nitrification, ordenitrification, the one or more containers each having a top, a bottomand a height dimension therebetween for receiving wastewater from thewastewater stream; a mixing system disposed at a level the containercapable of mixing the wastewater in the container at the required rate,the mixing system including an inlet for receiving recycled wastewaterand an outlet for discharging high-pressure wastewater into thecontainer; a pump having an inlet and an outlet, the inlet of the pumpconfigured to receive wastewater from substantially the bottom of thecontainer; and a solids/liquid separation system having an inlet influid communication with the outlet of the pump, a retentate outlet influid communication with the inlet of the mixing system, and a permeateoutlet; wherein the pump provides wastewater to the solids/liquidseparation system at a pressure and flow rate capable of satisfying thepressure and flow rate of both the solids/liquid separation system andthe mixing system.

Further, in part, the present invention can be a method of removingcontaminants from a wastewater stream. The method can include (1)admitting wastewater into a container having a height dimension andfilling the container to a level with wastewater; (2) mixing and/oraerating the wastewater in the tank with a mixing system and/or anaeration system, wherein at least one of the mixing and/or aerationsystems includes an inlet for receiving recycled wastewater/concentratedmixed liquor and an outlet for discharging the recycled mixed liquorinto the container; (3) treating the contaminants in the wastewater byat least one of aerobic digestion, anaerobic digestion, chemicaltreatment, nitrification, or denitrification; (4) pumping the wastewaterfrom the bottom of the container via a pump having an inlet and anoutlet; (5) providing the wastewater to a solids/liquids separationsystem in fluid communication with the outlet of the pump at a pressureand a flow rate sufficient to affect separation of the solids and theliquid in the wastewater stream within the solids/liquids separationsystem; (6) recycling the retentate to the inlet of the mixing and/oraeration system and (7) drawing off treated effluent.

The apparatus of the present invention is of a construction which isboth durable and long lasting, and which will require little or nomaintenance to be provided by the user throughout its operatinglifetime. The apparatus of the present invention is also of inexpensiveconstruction to enhance its market appeal and to thereby afford it thebroadest possible market. Finally, all of the aforesaid advantages andobjectives are achieved without incurring any substantial relativedisadvantage.

DESCRIPTION OF THE DRAWINGS

These and other advantages of the present invention are best understoodwith reference to the drawings, in which:

FIG. 1 is a somewhat schematic process flow diagram of a prior art MBRsystem used to remove contaminants from wastewater having a submergedmembrane system wherein a separate tank and/or membrane zone and both asuction pump and a recycle pump are required to achieve enough systempressure to affect adequate flow through the system;

FIG. 2 is a somewhat schematic process flow diagram of a prior art MBRsystem used to remove contaminants from wastewater having an externalmembrane system wherein a separate balance tank and both a supply pumpand a recycle pump are required to achieve enough system pressure toaffect adequate flow through the system;

FIG. 3A is a somewhat schematic process flow diagram of a wastewatertreatment system of the present invention illustrating a submerged tankwith a pump and solids/liquids separation system at grade level;

FIG. 3B is a somewhat schematic process flow diagram of an alternateembodiment wastewater treatment system of the present inventionillustrating a biological processing tank with a pump and solids/liquidsseparation system at grade level;

FIG. 4 is a schematic of a membrane configuration of the presentinvention, illustrating the membrane modules in a parallelconfiguration; and

FIG. 5 is a schematic of a prior art membrane configuration,illustrating the membrane modules in a series configuration.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

It will be appreciated by those skilled in the art that while thepresent invention is described with reference to utilization ofmembranes for solids/liquid separation after biological treatment, thepresent invention, and the inherent advantages achieved therewith, canbe utilized with and/or integrated into any wastewater treatment systemknown to those skilled in the art. Further, the present invention can beused with a wastewater treatment system incorporating any type ofsolids/liquid separation system including, but not limited to, membranetechnology (microfiltration, ultrafiltration, nanofiltration, reverseosmosis, biomedical filtration, etc.), barriers, centrifuges, cyclonesand/or any inline process to affect separation of solids from thetreated effluent.

It will further be appreciated by those skilled in the art that thepresent invention can be used and/or integrated into any new or existingwastewater treatment system including batch, semi-batch, continuousand/or discontinuous operations. The invention may be applied to anywastewater treatment system including aerobic or anaerobic systems,chemical treatment, phosphorous removal, nitrification, denitrification,or any treatment process known to those skilled in the art or acombination thereof. Moreover, it will be appreciated by those skilledin the art that the present invention may be readily incorporated intoany wastewater treatment scheme including those requiring both anoxicand aerobic tanks and/or zones. Thus, the present invention can be usedin schemes where single or multiple tanks and/or zones are used forwastewater treatment.

Prior to a discussion of the preferred embodiment of the presentinvention, it is useful to briefly discuss previously known activatedsludge waste processing systems including a solids/liquid separationsystem. In particular, FIGS. 1 and 2 illustrate conventionalconfigurations for membrane bioreactors (MBRs).

Referring to FIG. 1, a previously known MBR system 10 having a submergedmembrane configuration is illustrated. Wastewater containingcontaminants enters the system 10 from a source of wastewater 20, fromwhich it flows through feed line 22 through a screen 24, optionallyprovided to remove grit and/or larger particulate. The wastewater flowsinto a bioreactor, indicated generally at 26.

Weirs 28, 30 and 32 divide the bioreactor 26 into a number of treatmentzones, including an anoxic zone 34, an aeration zone 36, a membrane zone38 and treated water zone 40. It will be appreciated that separatevessels connected by conduits could be employed as an alternative to thebioreactor configuration illustrated in FIG. 1. The wastewater flowsinto the anoxic zone 34 which can be equipped with a mixer 42 fordenitrification. Effluent from the anoxic zone flows over the weir 28into the aeration zone 36.

Aeration zone 36 includes activated sludge, with the source of activatedsludge being from a recirculation of activated sludge produced duringthe waste treatment process; accordingly, the activated sludgeintroduced into the aeration zone 36 would generally be referred to asreturn activated sludge. Typically, the concentration of activatedsludge solids in conventional membrane bioreactors can range fromgreater than about 5,000 to about 15,000 milligrams per liter, dependingon the type of membrane utilized.

Hydraulic mixing and aeration occurs using a jet aeration system,indicated generally at 42. The jet aeration system 42 includes a pump 44for continually circulating/mixing the wastewater in the aeration zone36 and for ensuring sufficient oxygen transfer in the aeration zone 36.The jet aeration system 42 also includes a source of oxygen from ablower 46, air compressor or other source, as will be well known tothose skilled in the art, for providing the required oxygen and keepingthe solids in suspension. Either oxygen in air, pure oxygen or enrichedoxygen can be introduced into the bottom of the aerobic zone 36 usingthe aeration system. As is well known to those skilled in the art,aeration can cost up to about 70% or more of the total energy costs of awastewater treatment system.

It will be appreciated that aeration and mixing in the aeration zone 36can encompass two separate systems. This may be accomplished byproviding air to a compressor pump, which provides the compressed air tothe bottom of the aeration zone 36 (such as via coarse and/or finebubble diffusers) and providing a separate mechanical mixer. Other waysof introducing oxygen to the aeration zone 36 and/or mixing the contentsof the aeration zone 36 are well known in the art.

Aeration zone 36 may also include a pump 37 for pumping out wasteactivated sludge (WAS) from time to time, as the process calls for suchremoval.

From the aeration zone 36, the wastewater and contaminants flow into themembrane zone 38. The bioreactor 26 may be designed to permit wastewaterflow over the weir 30 from the aeration zone 36 to the membrane zone 38,or there may be a feed line provided from the aeration zone 36 to themembrane zone 38. In many conventional applications, the wastewater ispumped from the biological treatment zone to the membrane zone.

The membrane zone 38 includes one or more membrane modules 50 which canbe any type of separation membrane known to those skilled in the art.The membrane modules 50 are at least partially submerged inside themembrane zone 38. The membrane zone 38 also includes a membrane aeratorsystem 52, such as a fine and/or coarse bubble diffuser, for scouringthe membranes to inhibit fouling of the membranes 50. A source of airfrom a blower 54, air compressor or other source, is provided, as willbe well known to those skilled in the art. It will be appreciated thatthe aeration zone 36 and the membrane zone 38 may be provided with anintegrated aeration system designed to maximize oxygen transfer/bubbleformation in each of the zones where required by the given separationoperation.

A suction pump 56 is connected to the permeate outlet side of themembranes 50 to maintain a negative pressure on the permeate side of themembrane in order to achieve the required transmembrane pressure andflux across the membrane. Accordingly, wastewater is drawn through themembrane modules 50 by pump 56 such that the filtered effluent is pumpedout of the membrane zone 38 and into the treated water zone 40 through aline 60. (Transmembrane pressure is the driving force for membranefiltration and is the difference in pressure from the feed side of themembrane to the permeate side of the membrane. The flux is the flow ofpermeate water per unit surface area of the membrane and is a functionthe physical characteristics of the membrane, mode of operation and theoperating conditions.)

In order to clean the membrane modules 50, a backwash pump 62 isprovided to reverse the flow of permeate to the membranes to removesolids build-up on the surface of the membranes and restore uniform fluxacross the membrane. Cleaning can be performed at regular intervals orat a given reduction of flux or transmembrane pressure, as will be wellknown to those skilled in the art.

The retentate flows out of the membrane modules 50 and, accordingly, theconcentrated biomass is discharged back into the membrane zone 38. Itwill be appreciated that because the membrane zone 38 contains a highconcentration of solids (increased viscosity) due to the presence of theretentate, there is a greater likelihood of solids build-up on thesurface of the membrane.

A recycle pump 64 recycles the concentrated biomass from the membranezone 38 back to the anoxic zone 34. In conventional applications, itwill be appreciated that pump 64 must be sized to provide a sufficientflow to maintain the desired mixed liquor suspended solids (MLSS)concentration in the anoxic and/or aeration zones and/or to supplysufficient pressure of concentrated biomass back to the anoxic zone 34to achieve the desired mixing of the anoxic zone 34—especially where themixer 42 is not employed. The pump 64 may be controlled based on thelevel in the membrane zone, the anoxic zone and/or the aeration zone, orvia any other control scheme/mechanism known to those skilled in theart.

The treated effluent 68 flows out of the bioreactor 26 from the treatedwater zone 40 through the discharge line 66. The effluent 68 can bedirectly recycled for reuse (depending on the type of membrane modules50 utilized) or alternatively can be treated via tertiary operations.

Turning briefly to FIG. 2, another previously known MBR system having anexternal membrane configuration is illustrated. It will be noted thatthe MBR system illustrated in FIG. 2 includes additional pretreatments(mechanical, chemical and/or biological) of the incoming wastewaterprior to solids/liquid separation compared to the system illustrated inFIG. 1.

Wastewater containing contaminants enters a MBR system 80 from a sourceof wastewater 82, from which pumps 85 move the wastewater through ascreen 86, optionally provided to remove grit and/or larger particulate.A pump 84 pumps the wastewater into an equalization tank 88, provided tobalance the flows across the system—ensuring accommodation in the systemof peak flows. The wastewater is pumped via pump 90 into the first of aseries of bioreactors 92.

The bioreactor 92 may be any type of reactor known to those skilled inthe art including, but not limited to, anaerobic, anoxic and/or aerobic,depending on the processing requirements for the stream of wastewater. Achemical coagulant 94, such as alum, may be added to the bioreactor 92via line 96 to precipitate soluble phosphates to reduce phosphorousdischarge. The bioreactor 92 is provided with an aeration and/or mixingsystem 98 to ensure adequate mixing and oxygen transfer, where required.

The wastewater will flow from bioreactor 92 to one or more bioreactors,100 and 102. At least one of the bioreactors 92, 100 and/or 102 will bean aerobic treatment reactor including activated sludge, with the sourceof activated sludge being from a recirculation of activated sludgeproduced during the waste treatment process, as is well known to thoseskilled in the art. It will be appreciated that bioreactors 100 and 102will require adequate mixing and/or aeration provided by systems 104 and106, respectively.

Wastewater leaving the bioreactor 102 must be pumped via pump 108 to themembrane system (the solids/liquid separation system), indicatedgenerally at 110, through a line 112. Permeate exits the membrane system110 through a line 118 where it is collected in a tank 120. A pump 130is provided to pump the treated effluent from the tank 120 whenrequired.

The retentate flows out of the membrane system 110 and, accordingly, theconcentrated biomass is either recycled back to the bioreactor 92 vialine 122 and/or it is discharged into a balance tank 124, from which itis in turn fed along with the wastewater stream exiting the bioreactor102 to the membrane system 110. It will be appreciated that because theretentate contains a high concentration of solids, there is a solidsbuild-up in the tank 124, resulting in a higher concentration of solidsentering the membrane system 110.

Accordingly, a pump 114 is further provided to ensure propertransmembrane pressure and membrane flux are achieved in the membranesystem 110. It will be noted that the membrane system 110 is configuredwith membrane modules 116 in a series arrangement. As such, theconcentration of solids increases after each membrane module (see Athrough E, as indicated on FIG. 2 wherein the concentration of solids instream E is greater than that of stream D, which is in turn greater thanthat of stream C, which is in turn greater than that of stream B, whichis in turn greater than that of stream A). Thus, pump 114 must be sizedto ensure sufficient pressure to overcome the pressure losses in each ofthe membrane modules 116, the increase in viscosity exhibited thereinand to ensure adequate flow/pressure of recycled retentate back to thebioreactor 92.

Turning now to FIG. 3 (FIGS. 3A and 3B), the basic configuration for awaste processing system 300 of the present invention is illustrated. Asmentioned above, the most significant change over the systems describedin FIGS. 1 and 2 above, is that the system illustrated in FIG. 3combines the hydraulic mixing system and/or the aeration system of thebiological treatment portion of a wastewater treatment system with theinline solids/liquid separation process which, while eliminating theneed for redundancy in equipment, greatly reduces the energy required tooperate the system. It will be appreciated that while a simplifiedsystem of the present invention is illustrated, the system mayadditionally include any chemical treatment, phosphorous removal,nitrification, denitrification, settling tanks, clarifiers, extraction,etc. known to those skilled in the art. The invention may be used in anywastewater treatment system including not only biological treatment, butalso physical, chemical and/or thermal treatment of wastewater.

An aeration tank 302 of a height H is provided. A level controller 303may be provided in the tank 302 to determine the level of wastewatercontained therein. It will be appreciated that the aeration tank 302 iscapable of operating in batch mode, continuous mode, semi-continuousmode or discontinuous mode, all with equally high-quality results.Wastewater containing contaminants enters the system 300 from a sourceof wastewater 304 into the aeration tank 302. (For the purposes of thepresent description, wastewater in the tank 302 is illustrated at alevel L in FIG. 3). Activated sludge is also introduced into theaeration tank 302, with the source of activated sludge being from arecirculation of activated sludge accumulated from the solids/liquidseparation system (to be discussed below).

A jet aeration system 306 is included within the aeration tank 302 tohydraulically mix the wastewater in the aeration tank 302 and to provideoxygen to the bacteria in the tank, ensuring digestion of the wasteorganic matter. The jet aeration system 306 is preferably positionednear the bottom of the tank 302 to reduce settling of solids in thetank. The jet aeration system 306 includes at least one nozzle 308having at least one inlet 310 for receiving recirculated and/or recycledmixed liquor/concentrated biomass, as will be described in more detailbelow. The nozzle 308 has at least one outlet 312 where the pressurizedmixed liquor and/or entrained air exit the nozzle 308. At least oneblower 314 may be provided to introduce oxygen into the aeration tank302. Alternatively, oxygen may be introduced into the jet aerationsystem 306 by introducing compressed air into the bottom of the aerationtank 302 or by any means known to those skilled in the art.

The jet aeration system 306 preferably includes independent control ofmixing and oxygen transfer such that airflow rates can be regulatedwithout affecting mixing of the wastewater in the tank. As such,consistent with the broader aspects of the present invention, theprocess can also be operated in anaerobic, anoxic, or in a variableaeration mode where the aeration can be continuous, intermittent, or notused. Also, as noted previously, mixing and aeration conditions can bevaried to facilitate desired physical, chemical, and biologicalreactions, as will be well known to those skilled in the art. Further,it will be appreciated by those skilled in the art that aeration may notbe required by the wastewater treatment system—as such, the system 306may include hydraulic mixing only.

A pump 318 draws water through a water inlet 320 of the line 322,positioned in the aeration tank 302, to feed a solids/liquid separationsystem 324 through a line 326. The pump 318 may be any type of pumpknown to those skilled in the art capable of providing the requiredpressure and flow rate output as described in more detail below.

The solids/liquid separation system 324 (the “SLS”) is preferably aconfiguration of membrane modules (i.e. such as those utilized inconventional MBR systems shown in FIGS. 1 and 2). More preferably, theSLS 324 is a plurality of membrane modules arranged in a parallelconfiguration, as will be described in more detail below with referenceto FIG. 4. The SLS 324 may include microfiltration, ultrafiltration,nanofiltration, reverse osmosis, biomedical filtration, barriers,centrifuges, cyclones and/or any inline process to affect separation ofsolids from the treated effluent known to those skilled in the art.

Where the SLS utilizes membrane technology, the membrane modules arepreferably tubular, however, plate and frame, spiral wound, hollowfiber, and/or any membrane type or configuration known to those skilledin the art may be utilized. Indeed, where the waste stream includescertain contaminates and/or other types of organic or inorganic matter,specialty membranes may be required.

The feed pump 318 directs a flow of mixed liquor through the SLS 324 anda retentate/concentrated biomass stream exits the SLS 324 through line328 and is recycled back to the jet aeration system 306. The line 328can include a valve 325 to restrict flow through the SLS 324—wheretuning of the flow through the SLS may be warranted to maximize crossflow velocity of the wastewater across the surface of the membranes toprevent build-up of solids on the membrane, to maintain the desiredoperating pressure and/or to achieve the optimal membrane flux. Anoptional bypass line 327 and valve 329 can direct some wastewater flowfrom line 326 to line 328, bypassing the SLS, in order to achieve suchrequired flow rate, pressure and/or membrane flux in the system 300. Itwill be appreciated that the system of the present invention permitsoptimization of the cross flow velocity and/or the flux to membranemodules of the SLS 324 to scour the membranes to minimize fouling andensure a more uniform flow across the membranes.

The treated permeate/effluent stream 333 exits the SLS 324 through aline 330, including a flow monitoring device 332 and a control valve 334for monitoring and controlling the effluent flow out of the SLS 324. Theflow monitoring device 332 and the control valve 334 may be integratedwith the control of incoming wastewater 304 and/or the level controller303 in the aeration tank 302. It will be appreciated that solids removalin the solids/liquid separation system 324 can be further optimized toachieve a desired permeate flow Q_(p).

Consistent with the broader aspects of the present invention, the system300 may be controlled in any manner required known to those skilled inthe art. For example, the system 300 illustrated in FIG. 3 may beoperated in batch, semi-batch, continuous and/or discontinuousoperations. Further, such control can be dependent on thecontaminants/constituents of a given waste stream to be treated.Accordingly, control of the system can include one or more processvariables including, but not limited to, solids concentration, oxygendemand (DO and/or BOD), TOC, pH, conductivity, ORP, specific contaminantconcentrations, temperature, operational pressures, flow rates, etc., aswill be well known to those skilled in the art. For example, allowingthe DO to drop to less than a certain level before activating anaeration scheme is one of many common control schemes utilized fornitrification. Such control schemes/algorithms are well known to thoseskilled in the art.

In addition, consistent with the broader aspects of the presentinvention, the wastewater treatment system 300 of present invention isillustrated in FIG. 3A such that the tank 302 is beneath grade and thepump 318 and the solids/liquids separation system 324 are atsubstantially grade level. However, it will be appreciated that thepresent invention may be arranged and configured in any orientationprovided preferably that the pressure head of the liquid in the tank canbe utilized to, at least partially, drive the solids/liquid separation.As such, the present invention can include the aeration tank 302, thepump 318 and the SLS 324 positioned at substantially grade level, asillustrated in FIG. 3B (where like reference numerals in FIG. 3B referto like parts of FIG. 3A).

Accordingly, as illustrated in FIGS. 3A and 3B, the wastewater treatmentsystem of the present invention integrates the feed pump 318 of the jetaeration system 306 with the SLS 324 such that the solids/liquidseparation system 324 does not require an independent suction pump,permeate pump, recirculation pump and/or a supply pump to drivewastewater through the membrane/SLS.

As also illustrated in FIGS. 3A and 3B, in certain preferred embodimentsof the present invention, the pump 318 is arranged and configured toutilize the pressure head of the wastewater in the aeration tank 302 tomaintain the required transmembrane pressure for the solids/liquidseparation system. In order to achieve the pressure P_(A) and flow rateQ_(A) of concentrated mixed liquor out of the SLS 324 required for thejet aeration system 306, the pump 318 need only account for the pressureloss across the membrane system 324, any loss associated within the jetaerator nozzle(s) 308 in the jet aeration system 306 and any static liftrequired to move the wastewater above the wastewater level L in theaeration tank 302, illustrated in FIG. 3A (or, alternatively, any lossassociated with moving the wastewater above the tank floor, asillustrated in FIG. 3B). As such, the present invention provides asystem and method for treating wastewater in which significant energysavings can be achieved by minimizing system pressure generation/fluidpumping requirements.

As will be well known to those skilled in the art, there may beadditional process equipment located between the discharge outlet of thepump 318 and the SLS 324. For example, additional screens, centrifuges,or pretreatments may be included in the process. As such, the pump 318will account for such additional system losses, while maintaining aconstant pressure on the SLS 324.

Further, the present invention eliminates the need to include abalancing/equalization tank and/or a membrane tank/zone. In particular,because the concentrated mixed liquor is recycled to the aeration tank302, and the membrane modules of the SLS 324 are external from the tank,the tank 302 can be sized to function as a balance tank and/orequalization tank for the system—absorbing peak flows and/or peak MLSSconcentrations in the system, with the level L of wastewater in the tankbeing maintained at an optimal level L to provide sufficient head todrive the solids/liquid separation system. Elimination of a balance tankor zone reduces the footprint of the present system over prior artsystems.

As such, the recycled, concentrated biomass stream entering the tank 302through the jet aeration system 306 is combined with the contents of theaeration tank 302 to provide a stream of wastewater to the SLS 324having a lower, more uniform concentration of solids than that of theentering recycled stream. In this way, the concentration of solidssupplied to the SLS 324 from the aeration tank 302 is lower than that ofprior art systems that require a smaller membrane tank or balance tank,and that recirculate at least a portion of highly concentrated retentatedirectly back into the membrane system. Accordingly, the presentinvention inhibits fouling by reducing the level of solids at themembrane surface and providing a more uniform concentration of solidsacross the membrane over the prior art. In addition, it will be notedthat because the present invention reduces fouling of the membrane andprovides a constant pressure across the membrane, the system of thepresent invention can provide a higher, more uniform rate ofpermeability.

It can be seen that the present invention is a clear advantage over thetraditional MBRs illustrated in FIGS. 1 and 2. First, each of the priorart systems require a pump(s) to force/draw wastewater through themembrane modules and require a recycle pump(s) for mixing/sludge recycleof the return basins/tanks. Specifically, the present invention can beused to eliminate the suction pump 56, the recycle pump 64 and anyassociated monitoring and control devices of the submerged MBR systemillustrated in FIG. 1. Further, the present invention can be used toeliminate at least one of the pumps 90, 108 and 114 of the external MBRillustrated in FIG. 2.

Indeed, as illustrated in FIGS. 3A and 3B, the present inventioneliminates this duplicate requirement by operating the system in asubstantially “closed loop” manner, wherein a pump (such as pump 318 ormultiple pumps configured similar to pump 318) may be used to supplyboth the mixing system and the SLS—taking advantage of the pressure headof the wastewater in the biological treatment tank to operate at ahigher system pressure. Ergo, the pump 318 accounts for SLS and jetaeration system losses, dynamic/frictional losses and any static liftlosses associated with placement of the pump relative to the SLS system.Accordingly, the wastewater treatment system of the present inventionuses less energy and is less expensive to operate than conventionalwastewater treatment systems. In addition, with the elimination of apumping system and/or one or more level, flow or pressure controlsystems, the present invention is less expensive to purchase, installand maintain over prior art systems.

Further, because the present invention eliminates the need for a balanceor equalization tank, such as those illustrated in FIGS. 1 and 2, thepresent invention occupies a smaller footprint than conventional MBRsystems. In particular, the present invention can be used to eliminatethe membrane zone 38 and/or the treated water zone 40 of the systemillustrated in FIG. 1—by moving the SLS external to the biologicaltreatment system, as in the present invention, and utilizing abiological treatment zone (such as the anoxic/aeration zone) as thebalance/equalization tank. Likewise, the present invention can be usedto eliminate at least one of the tanks 88, 124 and 120 of theside-stream MBR illustrated in FIG. 2.

In addition, a system in accordance with the present invention canoperate at a higher static system pressure, due to the hydrostatic headof the wastewater, over traditional wastewater systems. Increasing thepressure under which the bioreactor aeration system operates alsoincreases the amount of oxygen that can be dissolved in the water.Accordingly, the present invention can utilize a higher/taller aerationtank, if desired, than current systems, since oxygen transfer is alimitation on the efficiency of current systems.

Moreover, the higher separation force that is possible with the systemof the present invention allows higher activated sludge solids levels tobe utilized, allowing for a smaller biological volume to be utilized,and therefore, a smaller process footprint to be utilized overconventional activated sludge systems. In turn, high MLSS concentrationsand low SRT promote other numerous process benefits including, but notlimited to, stable operation, complete nitrification, and reducedbiosolids production. It will be appreciated that the wastewatertreatment system of the present invention has many additionaladvantages, as will be apparent to those skilled in the art.

As recited herein, it will further be appreciated that while asimplified system has been illustrated, the present invention can beused, with one or more of the aforementioned advantages, on any existingsystem, such as those illustrated in FIGS. 1 and 2, to eliminateredundancy in equipment and reduce energy requirements. Accordingly,consistent with the broader aspects of the present invention, the system300 may be modified in configuration to account for any existing systemor landscape (at grade or above or below grade). Preferably, thewastewater treatment tank and the SLS are configured to take advantageof the hydraulic head of the wastewater and/or the pumping energyalready required by at least one of the mixing and/or aeration systemsin the wastewater treatment configuration.

Turning next to FIG. 4, another aspect of the present invention isdisclosed, including an improved membrane configuration 500 for use inthe hydraulically integrated wastewater treatment system of the presentinvention and/or for use in any conventional membrane bioreactor. Itwill be apparent that the solids/liquid separation system 324illustrated in FIG. 3 is preferably of or similar to the membranefiltration configuration 500 illustrated in FIG. 4. (For the purposes ofthe following discussion, like numbers will refer to like parts).

In FIG. 4, a plurality of membrane modules 502A, 502B, 502C and 502D arearranged horizontally in a parallel configuration with respect to amembrane feed pump 318 (e.g., membrane feed pump corresponding to pump318 in FIG. 3). Preferably, each of the membranes 502A-D are tubularmembranes. (However, the modules 502A-D may contain any type of membraneknown to those skilled in the art). The retentate/concentrated biomassexits each module 502 A-D through lines 504 A-D, respectively, whichwill be preferably joined to form line 328 (in FIG. 3), to feed the jetaeration system 306 or other mixing/aeration system of the wastewatertreatment system 300 of the present invention. Permeate exits eachmodule 502 A-D through lines 506 A-D, respectively, which will bepreferably joined to form effluent line 330.

The pressure and flow rate at the outlet of the pump 318 for supplyingthe membrane modules 502A-D is a pressure P₁ and a flow rate Q₁. It willbe appreciated that, in parallel, each module is supplied with awastewater stream having the same pressure (P₁), flow rate (Q₁) andsolids concentration (C₁). Accordingly, where each of the membranes502A-D are the same type and/or have substantially the same pressureloss/transmembrane pressure associated with driving the fluid throughthe membrane, the pressure P₂, flow rate Q₂ and solids concentration C₂of the retentate/concentrated biomass stream exiting each of themembrane modules 502A-D will be substantially similar for each module502A-D. Likewise, the pressure P_(p), flow rate Q_(p) and solidsconcentration C_(p) of the permeate/effluent streams exiting each of themembrane modules 502A-D will be substantially similar for each module502A-D.

For comparison, FIG. 5 illustrates a membrane module configuration 600of the prior art, wherein the membrane modules 602 A-D are configured inseries. In this configuration, the pressure and flow rate at the outletof the pump 601 for supplying the membrane modules 602 A-D is a pressureP₁, a flow rate Q₁ and a solids concentration C₁. However, unlike thepresent invention, the solids concentration C₂ through C₅ exiting eachmodule 602A-D through lines 604A-D, respectively, increases with eachpass—as permeate is withdrawn from each module 602A-D through lines606A-D, respectively.

Thus, the feed streams C₁ to C₄ increase progressively in viscosityacross the system, each membrane from 602A to 602D exhibits aprogressively thicker solids layer build-up on the membrane surface.Accordingly, the cross flow velocity decreases, the transmembranepressure and flux across the membrane increases, and the permeate flowrate (Q₆ though Q₉) decreases from module 602A to 602D. As such, themembranes 602A-D are more likely to foul than the membranes 502A-Dillustrated in FIG. 4. More frequent fouling of the membranes requiresmore frequent membrane cleaning, and more frequent replacement ofmembranes. (Where one or more of the membranes experiences foulingadditional pressure is required to achieve a given permeate flowrate—forcing the membranes to function outside their normal flux range.)

In addition, because the permeate flow rates achieved (Q₆ though Q₉)also decrease progressively, as the solids concentration and pressureincreases from 602A to 602D, the prior art configuration illustrated inFIG. 5 is limited in the amount of flow that the system can process.Further, the pump 601 must account for the pressure loss across eachmodule 602A-D (rather than the loss of a single module, as in theparallel configuration), and therefore, utilizes more energy than theparallel configuration illustrated in FIG. 4.

The membrane configuration 500 of the present invention of FIG. 4includes the pump 318, sized to achieve the pressure and flow raterequired by the jet aeration system or other mixing/aeration system,which can supply high cross flow velocities uniformly across each of themembrane modules such that each module operates at substantially thesame flux rate thereby providing less fouling and greater permeate flowrate over the configuration 600 illustrated in FIG. 5. By maintaining ahigh cross flow velocity, the membrane configuration 500 of the presentinvention requires less downtime for cleaning and maintenance.

Moreover, in conjunction with the wastewater processing systemillustrated in FIG. 3, the membrane configuration 500 illustrated inFIG. 4 further reduces the cost of operation and maintenance of thesystem. Specifically, the system 300 of the present invention canoperate at higher overall solids concentrations over conventionalsystems with a lower overall sludge yield.

Although the foregoing description of the present invention has beenshown and described with reference to particular embodiments andapplications thereof, it has been presented for purposes of illustrationand description and is not intended to be exhaustive or to limit theinvention to the particular embodiments and applications disclosed. Itwill be apparent to those having ordinary skill in the art that a numberof changes, modifications, variations, or alterations to the inventionas described herein may be made, none of which depart from the spirit orscope of the present invention. The particular embodiments andapplications were chosen and described to provide the best illustrationof the principles of the invention and its practical application tothereby enable one of ordinary skill in the art to utilize the inventionin various embodiments and with various modifications as are suited tothe particular use contemplated. All such changes, modifications,variations, and alterations should therefore be seen as being within thescope of the present invention as determined by the appended claims wheninterpreted in accordance with the breadth to which they are fairly,legally, and equitably entitled. It should also be noted that the termmixing/aeration system as used herein, including in the appended claims,refers to any system that provides a mixing function, or an aerationfunction or both mixing and aeration functions for wastewater treatmentas described herein. Furthermore, reference to the bottom of awastewater treatment container as used herein, including in the appendedclaims, refers to any position approximately at or near the bottom ofsuch a container.

1-14. (canceled)
 15. A method of treating wastewater, comprising (a)admitting wastewater into a wastewater treatment container having a top,a bottom, and a height dimension therebetween and filling the wastewatertreatment container to a level with wastewater; (b) mixing and/oraerating the wastewater in the wastewater treatment container with amixing/aeration system positioned below the level of wastewater in thewastewater treatment container and including an inlet for receivingretentate wastewater and an outlet for discharging retentate wastewaterinto the wastewater treatment container; (c) treating the wastewater inthe wastewater treatment container; (d) providing the wastewater fromthe wastewater treatment container to a solids/liquids separation systemat a pressure and flow rate sufficient to affect separation of solidsand the liquid in the wastewater stream within the solids/liquidsseparation system, the solids/liquid separation system having aretentate outlet; (e) recycling the retentate from the solids/liquidseparation system to the inlet of the mixing/aeration system; and (f)drawing off treated effluent from the solids/liquid separation system.16. The method of claim 15 wherein treating the wastewater in thewastewater treatment container includes treating the wastewater in thewastewater treatment container using at least one of the wastewatertreatment methods selected from the group of wastewater treatmentmethods consisting of aerobic digestion, anaerobic digestion, anoxicdigestion, phosphorous removal, chemical treatment, nitrification anddenitrification.
 17. The method of claim 15 wherein providing thewastewater from the wastewater treatment container to the solids/liquidseparation system includes pumping the wastewater using a pump having aninlet in fluid communication with the wastewater treatment container andan outlet in fluid communication with the solids/liquids separationsystem.
 18. The method of claim 17 wherein the pump inlet is in fluidcommunication with the bottom of the wastewater treatment container. 19.The method of claim 15 wherein the solids/liquid separation systemincludes a permeate outlet separate from the retentate wastewater outletthereof.
 20. The method of claim 15 and further comprising creating,with a pumping system, a pressure differential across themixing/aeration system and the solids/liquid separation system to movetreated wastewater from the wastewater treatment container to the inletof the solids/liquid separation system and retentate wastewater from theoutlet of the solids/liquid separation system to the inlet of themixing/aeration system and out of the outlet of the mixing/aerationsystem into the wastewater treatment container.
 21. The method of claim20 wherein creating, with a pumping system, a pressure differentialincludes coupling the pumping system to move treated wastewater fromapproximately the bottom of the wastewater treatment container andwherein the pumping system and the solids/liquid separation system areelevated with respect to the bottom of the wastewater treatmentcontainer.
 22. The method of claim 20 wherein creating, with a pumpingsystem, a pressure differential includes coupling the pumping system tomove treated wastewater from approximately the bottom of the wastewatertreatment container and wherein the pumping system and the solids/liquidseparation system are at approximately the same level as the bottom ofthe wastewater treatment container.
 23. The method of claim 15 whereinthe outlet of the solids/liquid separation system is coupled in fluidcommunication with the inlet of the mixing/aeration system without apumping device provided therebetween.
 24. The method of claim 15 whereinthe solids/liquid separation system is a solids/liquid separation systemselected from the group of solids/liquid separation systems consistingof membrane technology, barrier, centrifuge, and cyclone solids/liquidseparation systems.
 25. The method of claim 15 wherein the solids/liquidseparation system includes a membrane technology system selected fromthe group of membrane technology systems consisting of microfiltration,ultrafiltration, nanofiltration, reverse osmosis, and biomedicalfiltration systems.
 26. The method of claim 15 wherein the solids/liquidseparation system includes a plurality of membrane modules arranged in aparallel configuration.
 27. The method of claim 26 wherein the pluralityof membrane modules are arranged horizontally in a parallelconfiguration.
 28. The method of claim 15 wherein the solids/liquidseparation system includes a plurality of membrane modules arranged in aseries configuration.
 29. The method of claim 15 wherein themixing/aeration system is a jet aeration system.
 30. The method of claim15 wherein the wastewater treatment container is a wastewater treatmentcontainer selected from the group of wastewater treatment containersconsisting of an aeration tank, an anoxic treatment vessel, an anaerobictreatment vessel, a phosphorous removal tank, a chemical treatment tank,a nitrification tank, and a denitrification tank.
 31. A method oftreating wastewater, the method comprising: (a) admitting wastewaterinto a wastewater treatment container having a top, a bottom, and aheight dimension therebetween and filling the wastewater treatmentcontainer to a level with wastewater; (b) mixing and/or aerating thewastewater in the wastewater treatment container with a mixing/aerationsystem positioned below the level of wastewater in the wastewatertreatment container and including an inlet for receiving retentatewastewater and an outlet for discharging retentate wastewater into thewastewater treatment container; (c) treating the wastewater in thewastewater treatment container using at least one of the wastewatertreatment methods selected from the group of wastewater treatmentmethods consisting of aerobic digestion, anaerobic digestion, anoxicdigestion, phosphorous removal, chemical treatment, nitrification anddenitrification; (d) pumping the wastewater from the bottom of thewastewater treatment container via a pump having an inlet and an outlet;(e) providing the wastewater from the wastewater treatment container toa solids/liquids separation system in fluid communication with theoutlet of the pump at a pressure and flow rate sufficient to affectseparation of solids and the liquid in the wastewater stream within thesolids/liquids separation system, the solids/liquid separation systemhaving a retentate outlet; (f) recycling the retentate from thesolids/liquid separation system to the inlet of the mixing/aerationsystem; and (g) drawing off treated effluent from the solids/liquidseparation system.
 32. A method for reducing energy required to treatwastewater, the method comprising combining a mixing and/or aerationsystem of a biological treatment portion of a wastewater treatmentsystem with a solids/liquid separation process.
 33. A method ofseparating liquids and solids in a wastewater stream, the methodcomprising providing wastewater to a solids/liquid separation systemincluding a plurality of membrane modules arranged in a parallelconfiguration.